Compact polyphase fuse

ABSTRACT

A polyphase fuse of reduced bulk having ribbon fuse links whose length exceeds the height of the individual chambers or compartments of the casing or housing of the polyphase fuse wherein the fuse links are located. The ribbon fuse links are conductively connected to terminal or conductor strips whose juxtaposed surfaces are-or may be-fully utilized for the arrangement of ribbon fuse links. The terminal strips are individually affixed to the housing of the fuse and insulating spacers between the terminal strips are dispensed with.

O Umted States Patent [151 3,671,910 Kozacka 1 June 20, 197 2 [54] COMPACT POLYPHASE FUSE 1,299,132 4/1919 Conant 337/295 x 3,319,027 5/1967 Hitchcock... ..337/265 X [72] Inventor. Nl redH erlck J. Kozacka, South Hampton, 2,209,823 7/1940 Lohausenw "337/293 X 3,394,333 7/1968 Jacobs, Jr. ..337/293 X [73] Assignee: The Chase-Shawmut Company, Newburyp Primary E.\'aminerJ. V. Truhe [22] Filed, 8 1970 Assistant Examiner-l. A. Schutzman AtlorneyErwin Salzer [21] Appl. No.: 96,110

[57] ABSTRACT [52] U.S.C| 337/146,337/l6l,337/256, A polyphasefuse f reduced l having ribbon fuse mks 337/295 whose length exceeds the height of the individual chambers or [51] Int. Cl. ..H0lh 71/20 compartments of the casing or h i g f the polyphase fuse [58] Field Search 16] wherein the fuse links are located. The ribbon fuse links are I Ci d conductively connected to terminal or conductor strips whose [56] Re erences te juxtaposed surfaces are-or may be-fully utilized for the ar- UNITED STATES PATENTS rangement of ribbon fuse links. The terminal strips are individually' afi'lxed to the housing of the fuse and insulating 3 l WllSOn spacers between the ten-nina] trips are dispensed 3,281,555 10/1966 Fister..... 1 2,287,553 6/ 1942 Floten ..337/295 9 Claims, 4 Drawing Figures N 9 It:

v s-v/fl I I E /I 90 11. {/11 FATHETEUJUH 20 1872 I u 1 i a 1. I

INVENTORS= FREDERICK J. KOZACKA BACKGROUND OF INVENTION Polyphase fuses are fuses wherein a plurality of fuse units are enclosed in a common casing orhousing. Each of the fuse units is intended to be inserted into one phase of a polyphase circuit. Polyphase fuses are often applied for back-up protection of other circuit-interrupting devices, i.e. to protect other circuit interrupting devices on occurrence of major fault currents exceeding their interrupting capacity. When polyphase fuses are provided for back-up protectionfor other circuit-interrupting devices, e.g. molded case circuit breakers, severe limitations are imposed upon the size thereof because both the other circuit interrupting device and its back-up fuse must be arranged in a given, limited space. To be more specific, polyphase fuses when applied in conjunction with other circuit-interrupting devices for whose back-up protection they are intended, ought to be flat, or of minimal height, in order not to require large panel areas. Polyphase fuses include generally a substantially prismatic casing of electric insulating material, subdivided by internal partitions into a plurality of separate chambers or compartments. Each of these chambers, or compartments, houses one of a plurality of fuse units.

It appears from what has been stated above that the height of these chambers, or compartments, ought to be minimized. The depth available for these chambers, or compartments, is not subject to critical restrictions.

In prior art polyphase fuses the height of the fuse-unitreceiving chambers, or compartments, slightly exceeds the space available in some instances. These prior art polyphase fuses have not the degree of compactness, and in particular have not the limited height, which they ought to have, to make it possible to apply such fuses under the most stringent space limitations.

The primary object of this invention is to fill the long-felt need for more compact polyphase fuses, and in particular for polyphase fuses of drastically reduced height, capable of carrying both relatively small and relatively large currents.

SUMMARY OF INVENTION Polyphase fuses embodying this invention include a substantially prismatic housing of an electric insulating material subdivided by partitions into a plurality of separate chambers each closed on all sides thereof except one side. There is a pulverulent arc-quenching filler in each of said plurality of chambers. The structure further includes a cover means for closing the plurality of chambers on the open side thereof. There is a pair of substantially parallel conductor strips in each of said plurality of chambers. Each of said pair of conductor strips is arranged at opposite surfaces of one of said plurality of chambers and extends from the open side thereof to the side thereof opposite said open side. Said pair of conductor strips in each of said plurality of chambers is conductively interconnected by a plurality of ribbon fuse links which are embedded in said arc-quenching filler. The length of each of said plurality of ribbon fuse links exceeds the spacing between said pair of conductor strips in each of said plurality of chambers.

The structure further includes fastener means for securing each of said pair of conductor strips to a portion of said housing immediately adjacent thereto to maintain said pair of conductor strips in spaced relation in the absence of additional insulating spacers interposed between said pair of conductor strips. The space between juxtaposed surfaces of said pair of conductor strips is unencumbered by additional insulating spacers for spacing said pair of conductor strips.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a somewhat diagrammatic isometric view of a polyphase fuse embodying this invention as seen from the rear end, or cover end, thereof;

FIG. 2 is a plan view of a fuse link forming part of the structure of FIG. 1;

FIG. 3 is a vertical section across the structure of FIG. 1 taken at right angles to the front surface to the rear surface of the structure of FIG. 1; and

FIG. 4 is a section along IV-IV of FIG. 3.

DESCRIPTION OF PREFERRED EMBODIMENT Reference character 1 has been applied to generally designate a substantially prismatic housing or casing of electric insulating material subdivided by internal partitions la into three separate chambers, or compartments lb, each closed at all sides thereof except one side, or except its rear side R. Casing l is preferably a molding of an appropriate synthetic resin. The three chambers lb are filled with a pulverulent arc-quenching filler, preferably quartz sand. Reference numeral 2 has been applied in FIGS. 3 and 4 to indicate this body of pulverulent arc-quenching filler. Cover means 3 are provided for closing the open sides of chambers, or compartments, lb. Cover means 3 are provided with partitions 3a arranged in registry with the partitions la of casing or housing 1. In other words, each of partitions la and each of partitions 3a are arranged in a common vertical plane. The partitions 3a in cover 3 subdivide the latter into three separate chambers, or compartments, 3b of which each communicates with but one of chambers, or compartments, lb, and is separated from all other chambers, or compartments, lb. The body of pulverulent arc-quenching filler 2 in each of chambers, or compartments, lb extends into one of the chambers, or compartments, 3b defined by cover 3. As a result of this geometry housing 1 and cover 3 define jointly three separate chambers 1b,3b of which each is filled with a separate body of pulverulent arc-quenching tiller 2. Cover 3 is screwed to housing 1 by four screw-threaded studs 4 shown in FIG. 1.

A pair of straight conductor strips 5 is arranged in each of chambers, or compartments, lb. Each pair of conductor strips 5 is arranged at opposite surfaces of chambers lb and extends from the open or rear side of chambers, or compartments, lb to the side thereof opposite to the open side, which side is the front side of the polyphase fuse structure. The ends 5a of conductor strips 5 adjacent cover 3 are bent out of the plane of the remaining part of strips 5, and are intended to form terminals for connecting the polyphase fuse into a polyphase circuit. In FIG. 1 but the inside of one of the three chambers lb is fully shown, and but one pair of conductor strips 5 is fully shown. The internal arrangement of parts is the same in all three chambers lb and the conductor strips 5 in all three chambers are supposed to have bent ends to be used as terminals, or connectors. Conductor strips 5 are held in position by means of screws 6 projecting through the top wall and through the bottom wall of easing, or housing, I. The outer ends of screws 6, i.e. the heads thereof, may be covered with an insulating material or sealing material to preclude physical contact with any part, or parts, which have a potential above ground potential. These insulating seals have not been shown in the drawings.

A plurality of ribbon fuse links 7 interconnects conductively each pair of conductor strips 5. Fuse links 7 are embedded in arc-quenching filler 2. The length of each fuse link 7 exceeds the spacing between the pair of conductor strips 5 which are conductively interconnected by it, and each of fuse links 7 enclose acute angles a with the conductor or terminal strips 5 which are conductively interconnected by it. The conductor or terminal strips 5 in each of chambers, or compartments, 1b are conductively interconnected by two groups of fuse ribbon links 7. Each group of fuse links 7 includes a plurality of fuse links, i.e. three fuse links 7. The constituent fuse links 7 of each group have the same slant. The constituent fuse links of rear side R of each chamber, or compartment, lb to the front side F thereof. In other words, the rear ends of one group of fuse links 7 are at the level of a top conductor or terminal strip 5, and the rear ends of the other group of fuse links are at the level of a bottom conductor strip 5. The front ends of the first mentioned group of fuse links 7 are at the level of a bottom conductor strip 5, and the front side of the last mentioned group of fuse links is at the level of a top conductor strip 5. Ribbon fuse links 7 pertaining to different groups are separated relatively far from each other, thus minimizing the danger of merger of fulgurites taking the place of fuse links 7 upon blowing of the polyphase fuse. As shown in FIGS. l and 3 there is a cross-over region of the fuse links 7 pertaining to one group of fuse links 7 with the fuse links 7 pertaining to the other group of fuse links. While the spacing between the constituent fuse links 7 of the two groups of fuse links is smallest at this crossover region, the dielectric recovery of the arc gaps formed upon blowing of the polyphase fuse is satisfactory under the most adverse interrupting conditions on account of the length of the fuse links and the wide spacing of both groups of fuse links 7 along the preponderant portion of their length.

Each group of fuse links comprising three fuse links 7 is formed by one single integral stamping of sheet metal (silver) which includes a pair of parallel bars 7a of sheet metal of which each is conductively connected to one of a pair of conductor strips 5 in one of chambers, or compartments, lb. The stamping further includes a plurality of parallel ribbon sections 7 of sheet metal having a length exceeding the spacing of a pair of bars 70 and enclosing acute angles a with bars 7a. FIG. 2 shows such a stamping including bars 7a and ribbon fuse links 7.

Each conductor strip 5 is provided with a pair of grooves 50 extending parallel to the edges of conductor strips 5. The grooves 50' of each pair of strips 5 are arranged on the juxtaposed surfaces of the fonner and the stampings of FIG. 2 are inserted into pairs of juxtaposed grooves 5a in conductor strips 5.

Cover 3 is provided with three apertures 3c for filling the three chambers, or compartments, lb,3b formed by housing or casing l and by cover 3 with pulverulent arc-quenching filler. Each aperture 30 is sealed by a plug 8 which may be formed by a cured synthetic resin, eg, an epoxy resin.

The front side F of housing, or casing, l is provided with three apertures 1c having a relatively large diameter. The front wall of housing 1 forms integral hollow projections 1d each extending into one of chambers, or compartments, 1b. The aforementioned hollow projections 1d are preferably in the shape of solids of revolution, and each projection ld has a relatively small aperture 1e at the innermost end thereof, i.e. in the end thereof projecting farthest into one of chambers, or compartments, lb. A spring biased blown fuse indicator is arranged in the space between apertures 1c and 12. The blown fuse indicator includes indicating button 9, helical biasing spring 9a, spring supporting cap 9b, and tie rod 90. Tie rod 90 has an axially outer end affixed to indicating button 9 and an axially inner end which is flattened and arranged inside of hollow projection 1d. Reference numeral 10 has been applied to indicate a restraining wire conductively interconnecting conductor strips 5. Restraining wire 10 is substantially V-shaped and the converging end thereof extends through aperture le into hollow projection Id and is threaded through a hole provided in the axially inner flattened end of tie rod 90. The aperture 1e in hollow projection 1d is sealed by a body of sealing paste which retains its paste-like consistency. Silicone grease is the preferred sealing paste since relatively high temperatures may occur at the location of aperture 1e.

Housing, or casing, 1 forms an assembly jig of fixture for assembling the parts intended to be arranged therein. First the conductor strips 5 are inserted into housing 1 and firmly held in position therein by screws 6, or other appropriate fastening means. Thereupon the stampings 7,7a are inserted into the grooves 5a of strips 5, and solder in paste form is inserted into the grooves 5a, which makes the assembly ready for induction soldering. During this process the casing 1 remains relatively cool, and the generation of heat occurs primarily at the location where it is intended to form solder joints. Thereupon some silicone grease is placed adjacent the apex of projection 1d on the inner surface thereof, and parts 9,9a,9b and 9c are moved into place, and the ends of restraining wire 10 are threaded through the aperture 12 in projection Id. The ends of restraining wire 5 may be affixed to conductor strips 10 by means of screws 11. Then cover 3 is attached to housing, or casing, 1 by means of screw threaded studs 4, and quartz sand 2 is filled into the three chambers, or compartments, lb,3b through the apertures 30 in cover 3. Finally apertures 3c are filled by sealing means 8.

This way of assembly polyphase fuses is superior to the more conventional way involving the insertion of pre-assembled fuse units, one for each phase, into a common casing or housing for the polyphase fuse. The aforementioned prior art method of insertion of pre-assembled fuse units each into a separate chamber of a common casing, or housing, requires the addition of spacing means between the pair of spaced conductor strips of each phase unit. Deletion of additional spacing means for the conductor strips decreases significantly the cost of manufacture since it reduces both the cost of material and of labor.

It will be apparent from the above that in the structure which has been disclosed, the casing, or housing, 1 forms the spacing means for spacing pairs of conductor strips 5, thus dispensing with the need of providing additional spacing means for each pair of conductor strips 5.

Upon blowing of the fuse fulgurites take the place of ribbon fuse links 7, causing a voltage to appear across strips 5. As a result, restraining wire 10 fuses and pins 9 are propelled forwardly by spring action.

It will be apparent from FIGS. 1,3 and 4 that the L-shaped I conductor or terminal strips 5 include an external portion 5a and an internal portion provided with systems of grooves 5a extending in a direction longitudinally thereof. The grooves 511 begin at the bends of of strips 5 and extend all the way to the end of the internal portions of strips 5, or to a point coextensive with the fuse ribbon links positioned most remotely from said bends. This feature is necessary to be able to load the fusible elements 7 or 7,7a, respectively, into the casing l and strips 5 after the latter have been inserted into, and affixed to, the casing 1. FIGS. 1,3 and 4 show also clearly that the space between the juxtaposed surfaces of the internal portions of strips 5 are unencumbered by insulating spacers generally used for spacing strips or bars 5 from one another. The space between the juxtaposed surfaces of strips or bars 5 is, therefore, entirely available for fuse link means and arc-quenching filler.

The blown fuse indicator means which have been disclosed above are not claimed as my invention. These means are claimed in the copending patent application of Kenneth W. Swain, filed Dec. 15, I970 Ser. No. 098,422 for Electric Low Voltage Fuse.

I claim as my invention:

1. A polyphase fuse including a. a substantially prismatic housing of electric insulating material subdivided by internal partitions into a plurality of separate chambers each closed on all sides thereof except one side; a pulverulent arc-quenching filler in each of said plurality of chambers; c. a cover means for closing said plurality of chambers on the open side thereof; a pair of substantially parallel spaced conductor strips in each of said plurality of chambers, each said pair of conductor strips being arranged at opposite surfaces of one of said plurality of chambers and extending from the open side thereof to the side thereof opposite said open side; e. a plurality of ribbon fuse links embedded in said arcquenching filler and conductively interconnecting said pair of conductor strips in each of said plurality of chambers, the length of each of said plurality of ribbon fuse links exceeding the spacing between said pair of conductor strips in each of said plurality of chambers; and

a fastener means for securing each of said pair of conduc- 5 tor strips to a portion of said housing immediately adjacent thereto to maintain said conductor strips in spaced relation by said housing and in the absence of additional insulating spacers interposed between said pair of conductor strips, the space between juxtaposed surfaces of said pair of conductor strips being unencumbered by additional insulating spacers for spacing said pair of conductor strips.

2. A polyphase fuse as specified in claim 1 wherein said cover means is provided with a plurality of sealed aperture means equal to the number of separate chambers formed inside said housing for filling said arc-quenching filler through said cover means separately into each of said plurality of chambers.

3. A polyphase fuse as specified in claim 1 wherein said cover means define a cavity for receiving said arc-quenching filler, said cavity being subdivided by internal partitions each arranged in registry with one of said internal partitions of said housing, and wherein said cover means is provided with a plurality of sealed apertures each establishing when open a assageway from the outside of said housing and cover means to one of said separate chambers of said housing.

4. An electric fuse including a. a housing of insulating material defining an elongated chamber;

b. a pair of substantially L-shaped terminal bars including an external portion projecting away from said housing and an internal portion arranged inside said housing;

c. fusible elements inside said housing conductively interconnecting said internal portion of said pair of terminal bars;

d. a pulverulent arc-quenching filler inside said housing embedding said fusible elements; and

e. fastener means for each of said pair of terminal bars individually affixing each of said pair of terminal bars to said housing, said fastener means leaving the space between juxtaposed surfaces of said internal portion of said pair of terminal bars unencumbered, and said pair of terminal bars being spaced from each other solely by said housing and additional insulating spacers arranged within the gap between said internal portion of said pair of terminal bars being excluded from said chamber.

5. An electric fuse as specified in claim 4 wherein said juxtaposed surfaces of said internal portion of said pair of terminal bars are provided with systems of continuous parallel grooves extending from the point where said pair of terminal bars are bent to be substantially L-shaped to the innermost end of each of said juxtaposed surfaces of said pair of terminal bars.

6. An electric fuse as specified in claim 4 wherein said fastener means are arranged substantially at interfaces formed between said internal portion of said pair of terminal bars and walls of said housing.

7. An electric fuse including a. a substantially prismatic housing of insulating material forming an elongated chamber; b. a pair of terminal strips having bends of substantially 90, one portion of each of said pair of strips projecting through an aperture in said housing from the inside to the outside thereof and another portion of said pair of strips being housed inside said chamber in abutting relation to juxtaposed walls thereof, said another portion of said pair of terminal strips being provided with systems of parallel continuous grooves at juxtaposed surfaces thereof; fusible element means inside said housing conductively interconnecting said another portion of said pair of strips, the ends of said fusible element means engaging said systems of grooves at said juxtaposed surfaces of said pair of terminal strips;

d. a pulverulent arc-quenching filler inside said chamber embedding said fusible element means; and e. fastener means for each of said pair of terminal strips individually affixing said another portion of each of said pair of terminal strips to a portion of the wall of said housing immediately adjacent thereto, said pair of terminal strips being spaced from each other by virtue of their support by said housing and the gap formed between said another portion of said pair of strips being unencumbered by spacing means of insulating material for spacing said pair of terminal strips. 8. A polyphase fuse including a. a substantially prismatic housing of electric insulating material subdivided by internal partitions into a plurality of separate chambers each substantially closed on all sides thereof except one side; b. a body of pulverulent arc-quenching filler in each of said plurality of chambers; c. a joint cover means for closing said plurality of chambers on the open side thereof; d. a pair of substantially parallel terminal bars in each of said plurality of chambers, each of said pair of terminal bars being arranged at opposite surfaces of one of said plurality of chambers and extending from the open side thereof to the side thereof opposite said open side, said pair of terminal bars in each of said plurality of chambers being individually affixed to said housing and spaced from each other solely by said housing to the exclusion of any additional spacing means arranged inside the gap space defined by juxtaposed surfaces of said pair of terminal bars, each of said juxtaposed surfaces of said pair of terminal bars in each of said plurality of chambers being provided with a plurality of parallel groove means extending in a direction longitudinally of said plurality of chambers; and a plurality of spaced ribbon fuse link means embedded in said arc-quenching filler and conductively interconnecting said pair of terminal bars in each of said plurality of chambers, the length of each of said plurality of ribbon fuse link means exceeding the spacing between said pair of terminal bars in each of said plurality of chambers, said plurality of fuse links means in each of said plurality of chambers being formed by a plurality of integral stampings each including in addition to a plurality of ribbon fuse links a pair of spaced terminal strips having edges engaging said plurality of groove means in each said pair of terminal bars in each of said plurality of chambers. An electric fuse including a. a housing of a synthetic resin defining an elongated cavity substantially closed at one side of said housing and open at the opposite side thereof; b. a pulverulent arc-quenching filler inside of said cavity;

. a cover closing the open side of said cavity; a pair of substantially parallel terminal bars arranged inside of and at opposite sides of said cavity and individually affixed to said housing, said pair of terminal bars being spaced from each other solely by said housing to the exclusion of any additional spacing means arranged inside the gap defined by juxtaposed surfaces of said pair of terminal bars, each of said juxtaposed surfaces of said pair of terminal bars being provided with a plurality of groove means extending in a direction longitudinally of said pair of terminal bars; and fuse link means conductively interconnecting said pair of terminal bars, said fuse link means including a plurality of spaced ribbon fuse links forming a plurality of current paths separated from each other by said pulverulent arcquenching filler and said fuse link means further including a plurality of pairs of terminal strips inserted with the longitudinal edges thereof into said plurality of groove means in said pair of terminal bars, each pair of said plurality of pairs of terminal strips being conductively interconnected by a plurality of said ribbon fuse links and jointly forming an integral stamping with said terminalstrip-interconnecting ribbon fuse links. 

1. A polyphase fuse including a. a substantially prismatic housing of electric insulating material subdivided by internal partitions into a plurality of separate chambers each closed on all sides thereof except one side; b. a pulverulent arc-quenching filler in each of said plurality of chambers; c. a cover means for closing said plurality of chambers on the open side thereof; d. a pair of substantially parallel spaced conductor strips in each of said plurality of chambers, each said pair of conductor strips being arranged at opposite surfaces of one of said plurality of chambers and extending from the open side thereof to the side thereof opposite said open side; e. a plurality of ribbon fuse links embedded in said arcquenching filler and conductively interconnecting said pair of conductor strips in each of said plurality of chambers, the length of each of said plurality of ribbon fuse links exceeding the spacing between said pair of conductor strips in each of said plurality of chambers; and f. a fastener means for securing each of said pair of conductor strips to a portion of said housing immediately adjacent thereto to maintain said conductor strips in spaced relation by said housing and in the absence of additional insulating spacers interposed between said pair of conductor strips, the space between juxtaposed surfaces of said pair of conductor strips being unencumbered by additional insulating spacers for spacing said pair of conductor strips.
 2. A polyphase fuse as specified in claim 1 wherein said cover means is provided with a plurality of sealed aperture means equal to the number of separate chambers formed inside said housing for filling said arc-quenching filler through said cover means separately into each of said plurality of chambers.
 3. A polyphase fuse as specified in claim 1 wherein said cover means define a cavity for receiving said arc-quenching filler, said cavity being subdivided by internal partitions each arranged in registry with one of said internal partitions of said housing, and wherein said cover means is provided with a plurality of sealed apertures each establishing when open a passageway from the outside of said housing and cover means to one of said separate chambers of said housing.
 4. An electric fuse including a. a housing of insulating material defining an elongated chamber; b. a pair of substantially L-shaped terminal bars including an external portion projecting away from said housing and an internal portion arranged inside said housing; c. fusiblE elements inside said housing conductively interconnecting said internal portion of said pair of terminal bars; d. a pulverulent arc-quenching filler inside said housing embedding said fusible elements; and e. fastener means for each of said pair of terminal bars individually affixing each of said pair of terminal bars to said housing, said fastener means leaving the space between juxtaposed surfaces of said internal portion of said pair of terminal bars unencumbered, and said pair of terminal bars being spaced from each other solely by said housing and additional insulating spacers arranged within the gap between said internal portion of said pair of terminal bars being excluded from said chamber.
 5. An electric fuse as specified in claim 4 wherein said juxtaposed surfaces of said internal portion of said pair of terminal bars are provided with systems of continuous parallel grooves extending from the point where said pair of terminal bars are bent to be substantially L-shaped to the innermost end of each of said juxtaposed surfaces of said pair of terminal bars.
 6. An electric fuse as specified in claim 4 wherein said fastener means are arranged substantially at interfaces formed between said internal portion of said pair of terminal bars and walls of said housing.
 7. An electric fuse including a. a substantially prismatic housing of insulating material forming an elongated chamber; b. a pair of terminal strips having bends of substantially 90*, one portion of each of said pair of strips projecting through an aperture in said housing from the inside to the outside thereof and another portion of said pair of strips being housed inside said chamber in abutting relation to juxtaposed walls thereof, said another portion of said pair of terminal strips being provided with systems of parallel continuous grooves at juxtaposed surfaces thereof; c. fusible element means inside said housing conductively interconnecting said another portion of said pair of strips, the ends of said fusible element means engaging said systems of grooves at said juxtaposed surfaces of said pair of terminal strips; d. a pulverulent arc-quenching filler inside said chamber embedding said fusible element means; and e. fastener means for each of said pair of terminal strips individually affixing said another portion of each of said pair of terminal strips to a portion of the wall of said housing immediately adjacent thereto, said pair of terminal strips being spaced from each other by virtue of their support by said housing and the gap formed between said another portion of said pair of strips being unencumbered by spacing means of insulating material for spacing said pair of terminal strips.
 8. A polyphase fuse including a. a substantially prismatic housing of electric insulating material subdivided by internal partitions into a plurality of separate chambers each substantially closed on all sides thereof except one side; b. a body of pulverulent arc-quenching filler in each of said plurality of chambers; c. a joint cover means for closing said plurality of chambers on the open side thereof; d. a pair of substantially parallel terminal bars in each of said plurality of chambers, each of said pair of terminal bars being arranged at opposite surfaces of one of said plurality of chambers and extending from the open side thereof to the side thereof opposite said open side, said pair of terminal bars in each of said plurality of chambers being individually affixed to said housing and spaced from each other solely by said housing to the exclusion of any additional spacing means arranged inside the gap space defined by juxtaposed surfaces of said pair of terminal bars, each of said juxtaposed surfaces of said pair of terminal bars in each of said plurality of chambers being provided with a plurality of parallel groove means extending in a direction longitudinally of said plurality of chambers; and e. a plurality of spaced ribbon fuse linK means embedded in said arc-quenching filler and conductively interconnecting said pair of terminal bars in each of said plurality of chambers, the length of each of said plurality of ribbon fuse link means exceeding the spacing between said pair of terminal bars in each of said plurality of chambers, said plurality of fuse links means in each of said plurality of chambers being formed by a plurality of integral stampings each including in addition to a plurality of ribbon fuse links a pair of spaced terminal strips having edges engaging said plurality of groove means in each said pair of terminal bars in each of said plurality of chambers.
 9. An electric fuse including a. a housing of a synthetic resin defining an elongated cavity substantially closed at one side of said housing and open at the opposite side thereof; b. a pulverulent arc-quenching filler inside of said cavity; c. a cover closing the open side of said cavity; d. a pair of substantially parallel terminal bars arranged inside of and at opposite sides of said cavity and individually affixed to said housing, said pair of terminal bars being spaced from each other solely by said housing to the exclusion of any additional spacing means arranged inside the gap defined by juxtaposed surfaces of said pair of terminal bars, each of said juxtaposed surfaces of said pair of terminal bars being provided with a plurality of groove means extending in a direction longitudinally of said pair of terminal bars; and e. fuse link means conductively interconnecting said pair of terminal bars, said fuse link means including a plurality of spaced ribbon fuse links forming a plurality of current paths separated from each other by said pulverulent arc-quenching filler and said fuse link means further including a plurality of pairs of terminal strips inserted with the longitudinal edges thereof into said plurality of groove means in said pair of terminal bars, each pair of said plurality of pairs of terminal strips being conductively interconnected by a plurality of said ribbon fuse links and jointly forming an integral stamping with said terminal-strip-interconnecting ribbon fuse links. 